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332

PRACTICAL ORGANIC CHEMISTRY

AgNOo, and the addition of caustic soda will cause the base to
separate (if insoluble) as solid or liquid, or, if the base is volatile,
will produce a strong ammoniacal smell. The further examination
of the base is the same as that described under § I, 2. Acid
chlorides are usually insoluble in water, but rapidly decompose,
and may pass into solution as the free acid, giving at the same
time free hydrochloric acid.
4. Contains Sulphur.-—It may be the sulphate of a base,
in which case the solution will give a precipitate with barium
chloride, and the process of examination is that described under
§ I, 2. Heat with dilute hydrochloric acid. The bisulphite
compound of an aldehyde or ketone will be decomposed and
sulphur dioxide evolved. An alkyl acid sulphate will also be
decomposed, and free sulphuric acid will be found in solution
(see Reaction, p. 54). Distil with dilute sulphuric acid, and
test the distillate for volatile aldehyde or ketone. /.-Bromo- and
/-nitro-phenylhydrazine are useful reagents (see § I, i). An
acid ester of sulphuric or sulphurous acid will also be decomposed
by dilute sulphuric acid, and the distillate may be tested for an
alcohol. If it is an aroinatic mlphonic acid, it may be distilled
in steam with the addition of cone, sulphuric acid, when
the hydrocarbon will distil (p. 292), or fused with caustic potash,
when the phenol will be obtained (p. 179). Thiourea will also
appear under this head, and should be looked for. Heat a little
of the substance to the melting-point for a minute, and test for
thiocyanate with KC1 and FeCl3.
§ "ll. SINGLE SUBSTANCES, INSOLUBLE OR
SLIGHTLYSOLUBLE IN HOT OR COLD WATER.—This
category includes the majority of organic compounds.
i. Contains only Carbon and Hydrogen, or Carbon,
Hydrogen, and Oxygen.
Liquids.—It may be a hydrocarbon (paraffin,olefine,aromatic)
higher alcohol (e.g.* amyl alcohol), aldehyde (e.g., benzaldehyde)
ketone (e.g., acetophenone) acid (e.g., valeric acid), ether', ester,
fihenol (e.g., carvacrol) phenol ether (e.g., an i sole).
Hydrocarbons.—The action of sodium when testing for the
elements wrll already have indicated the hydrocarbon by its
inertness. The immediate decolonisation of bromine water will
identify it as an unsaturated hydrocarbon. A paraffin may be
distinguished from an aromatic hydrocarbon by treating tlte